Imports System.Net
Imports System.Web
'http://api.bitly.com/v3/shorten?longUrl=エンコードURL&login=bit.lyのユーザ―名&apiKey=bit.lyのAPIキー&format=フォーマット

'エンコードURLには、JSの場合はencodeURIComponent()、PHPの場合はurlencode()を使用して、エンコードしたロングURLを指定します。 フォーマットには、戻り値の形式を指定します。JSON形式なら「json」、XMLなら「xml」を指定します。
'https://bitly.com/a/your_api_key 　でUsernameとAPIKEY取得

Public Class bitlyshort
    Const bitlyformat As String = _
"http://api.bitly.com/v3/shorten?longUrl={0}&login={1}&apiKey={2}&format=xml"

    Public Function Getbitlyshort(ByVal url As String, ByVal username As String, ByVal apikey As String)
        Try
            Dim strEncode As System.Text.Encoding = System.Text.Encoding.GetEncoding("UTF-8")
            Dim encodeurl As String = HttpUtility.UrlEncode(url, strEncode)
            Dim targeturl As String = String.Format(bitlyformat, encodeurl, username, apikey)
            Dim wc As New System.Net.WebClient
            Dim bitlyxml As String = wc.DownloadString(targeturl)
            Dim geturl As String = Xmltourl(bitlyxml)
            Return geturl
        Catch ex As Exception
            Return Nothing

        End Try

    End Function

    Private Function Xmltourl(ByVal bitlyxml As String) As String

        Dim xdoc As New System.Xml.XmlDocument()
        xdoc.LoadXml(bitlyxml)
        Dim status As System.Xml.XmlNodeList = xdoc.GetElementsByTagName("status_code")
        Dim url As System.Xml.XmlNodeList = xdoc.GetElementsByTagName("url")

        If status.Item(0).InnerText = "200" Then
            Return url.Item(0).InnerText
        Else
            Return Nothing
        End If
    End Function
End Class